With the increasing market demand for the third-generation display technology, the development and production of flexible OLEDs has become a hot area for the display industry. Wherein, the flexible encapsulation technology is directly related to the display life of OLED, which is one of the bottlenecks restricting the development of OLED. Currently, the flexible encapsulation mainly adopts a laminated structure of an inorganic layer-organic layer-inorganic layer, and the flexible encapsulation requires not only fully resisting the erosion of external water and oxygen, but also effectively covering particle contaminant, buffer bending, and the stress in the folding process which are unavoidable in the production process. For the inorganic layer, it is mainly used to block the erosion of external water and oxygen; while the organic layer is mainly used to cover the particle contaminant, buffer bending and stress during the folding process, which is unavoidable in the production process. Therefore, the organic layer is also called organic buffer layer.
The organic buffer layer in the encapsulation structure is usually realized by a technique such as flash distillation, inkjet printing (IJP), in which the inkjet printing method is shorter in process time and excellent in planarization effect. However, the material for preparing the organic layer is good in the fluidity and the boundary is not easy to control. Usually, a retaining wall (dam) is made outside the display region to block the uncontrollability of the ink boundary. Since the retaining wall is usually obtained by using the same metal mask in the preparation of the planarization layer and the pixel definition layer, the material of the retaining wall is an organic material, water vapor is easily penetrated, and in order to completely block the overflow of the organic layer material, at least two retaining walls are generally produced.
More importantly, if the material of the organic layer is hydrophilic and the material of the retaining wall is also hydrophilic, or the material of the organic layer is hydrophobic and the material of the retaining wall is also hydrophobic, the same hydrophilic/hydrophobic material in organic layer and the retaining wall will generate a surface mutual solubility, which will have a greater impact on the barrier effect of the retaining wall. It is necessary to increase the thickness of the retaining wall or provide a multi-layer retaining wall to achieve a better blocking function. Further, the boundary width of the outermost inorganic layer at the time of preparation is affected, at least the edge of the outermost retaining wall is required to ensure that the edge does not corrode by the water and oxygen quickly, which is disadvantageous for the design of the narrow frame.